Field of the Invention
Embodiments of the present invention generally relate to a micro-electromechanical system (MEMS) digital variable capacitor (DVC).
Description of the Related Art
Some MEMS DVC devices are based on a moveable MEMS plate with a control-electrode above (i.e., pull-up or pull-off or PU electrode) and below (i.e., pull-on or pull-in or pull-down or PD electrode) the moveable MEMS plate (i.e., movable electrode, plate electrode, cantilever), as shown schematically in FIG. 1. These electrodes are covered with a top and bottom dielectric layer. Additionally, there is an RF-electrode below the moveable MEMS element between or adjacent to the pull-down electrodes. Between the moveable plate and the RF-electrode there is a gap that is modulated by the voltages applied to either the PU or the PD-electrode. These voltages result in electrostatic forces, which pull the movable electrode either up or down in contact with the dielectric layers to provide a stable minimum or maximum capacitance to the RF-electrode. In this way the capacitance from the moveable plate to the RF-electrode can be varied from a high capacitance state Cmax when pulled to the bottom (See FIG. 2) to a low capacitance state Cmin when pulled to the top (See FIG. 3).
The RF signal present on the RF-electrode can couple to the PD-electrode through the dielectric layer, as shown in FIG. 4, resulting in electrostatic forces pulling on the movable electrode above it. The plate will deform due to these electrostatic forces which can result in a modulation of the Cmax by the RF-signal. This capacitance modulation leads to a harmonic distortion of the RF-signal.
Therefore, there is a need in the art for a MEMS DVC device with minimal or no harmonic distortion of the RF signal.